McCarthy's husband was killed by a gunman on the Long Island Railroad in 1993

(CNN) -- Surveillance video shows Tucson shooting suspect Jared Loughner walking up to Rep. Gabrielle Giffords at a constituent event and firing point blank at her face, the Washington Post reported Tuesday, citing two sources who have seen the videos.

The bullet from his 9mm Glock entered Giffords' head just above her left eye and exited from the back of her skull, the sources said.

Giffords is in serious condition at University Medical Center in Tucson. A second, unnamed victim is listed in good condition, the hospital said.

The videos showed that U.S. District Judge John Roll was killed while covering Giffords' district director Ron Barber, who was one of 13 people wounded in the January 8 shooting outside a Tucson supermarket, the Post's sources said. Six people, including Roll, were killed.

The sources told the Post that Loughner fired 32 rounds -- one more than his 31-round magazine held. Investigators believe the 32nd round was already in the weapon's chamber when he loaded the magazine.

Legislation banning the kind of multiple-round ammunition magazine used shootings was introduced Tuesday evening in the U.S. House.

Democratic Rep. Carolyn McCarthy of New York introduced the measure banning "large capacity" ammunition magazines, defined as those that hold more than 10 rounds. Sen. Frank Lautenberg, D-New Jersey, will introduce similar legislation in the Senate later this month.

"I know what it's like to have tragedy brought to your life in a split-second by a madman with high-capacity ammunition magazines," said McCarthy, whose husband was killed and son seriously wounded by a gunman on the Long Island Railroad in 1993. "I'm working to stop it from happening again."

"This nation has come together before to support this simple, common-sense measure, and it is the law in several states right now," she said Tuesday afternoon. "It is a small sacrifice that law-abiding gun owners can make once again in order to increase everyone's safety."

The manufacture and sale of new large-capacity magazines were outlawed under the assault weapons ban that was in place from 1994 until 2004, when Congress let it expire under President George W. Bush. McCarthy's legislation would also apply to previously manufactured magazines.

The measure includes exemptions for law enforcement and security purposes.

"High-capacity gun magazines are tools for murder," Lautenberg said. "This common-sense legislation would make it more difficult for someone to carry out a killing spree."

The Washington Post report says that Loughner, 22, shot Giffords from about two or three feet away and then turned to his left, firing on people -- not shown in the video -- who were seated or standing in line for the event. Then, the sources told the paper, he turned back to his right and shot Barber, 65.

"Judge Roll starts to push Barber down on the ground and lay on top of Barber, and they start to scamper under the table, but Roll is on top," one source said, according to the newspaper. "At that point, you can see the suspect shoot Roll. Roll gets shot in the back, then he sort of appears halfway on the other side of the table. He starts to look over his right shoulder, and then he lays back down. It took out his aorta is what the autopsy showed."

The sources said that video ends at that point, but others show Loughner firing until he runs out of ammunition, when he was tackled by people attending the event.

Meanwhile, a law enforcement official said Tuesday that federal and local authorities have conducted more than 300 interviews with family members, friends, neighbors and others as part of the probe into the shooting.

The number of federal personnel deployed in the investigation hit a high of about 250 people, including agents, analysts and evidence response teams, the official said.

The FBI has substantial resources in Arizona and was able to supply about 200 of those people, the official said. An additional 50 people came from FBI offices in Washington, D.C., and Quantico, Virginia, and also from other federal law enforcement agencies such as the U.S. Marshals Service, the U.S. Capitol Police and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, the official said.

The total number has now dropped to less than 250 people, the official said.

Local law agencies had assigned about 130 people to the investigation as well, but the official didn't know the current figure.

The Washington Post reported the parents of alleged gunman Loughner have not been able to provide much information and have told authorities they had little recent contact with Jared. When asked about this, the official said the parents have been cooperative, but did not assess how useful their information has been in the investigation.

A federal judge entered a plea of not guilty Monday on behalf of Jared Lee Loughner to three counts of attempted murder in the mass shooting that wounded U.S. Rep. Gabrielle Giffords earlier this month.